It is known that soybeans can be used to produce a healthy, protein-rich beverage, usually by powdering a selected portion of the soybean and mixing the powder with hot water. However, numerous problems have been identified with conventional processing methods. For example, many processes use only a portion of the soybean, or a certain amount of waste is produced even where the process starts with whole beans. The latter can be seen, for example, in U.S. Pat. No. 4,971,825 to Kitazume et al., which discloses a process where the whole bean is used initially, but a “bean cured refuse” waste product is generated. This waste of protein and fibre is undesirable.
Another identified issue is the negative impact of heat and oxidation on flavour and appearance of the final beverage product. For example, U.S. Patent Application No. 20120183645 to Kim discloses a process for producing a soy milk beverage using whole beans. The process employs a heat chamber to metamorphose starch in the beans into dextrin, then the beans are ground into a powder, which powder is then mixed with water and subsequently homogenized and sterilized to generate the final product. The process, however, roasts the soybeans, and this oxidative process can introduce undesirable colours and flavours. For a beverage intended for human consumption, this is clearly problematic.
Various responses have been proposed to address the undesirable colours and flavours introduced by conventional processes. For example, PCT Application No. PCT/BR2006/000179 to Kai discloses a soy beverage process involving the use of pectinase enzyme to reduce unpleasant odour. The introduction of enzymes has become a well-known practice in soybean beverage production: see, as a further example, Canadian Patent No. 1,083,879 to Hsieh et al. which discloses a process for making a soybean beverage wherein whole beans are ground and then slurried with hot water, followed by the addition of enzymes. While enzyme additives do address the issue, they add to the cost of soybean beverage production and are therefore a less desirable solution.
Further, it has been found that soybeans incorporate trypsin inhibitors, which negatively impact digestibility of soybean beverages and reduce the body's ability to extract nutritive value from the beverage. While some prior art processes seek to remove the trypsin inhibitors during beverage processing, many others fail to recognize or address this significant problem at all.
What is needed, therefore, is a simplified method and apparatus for producing a soybean-based beverage, which reduces waste, limits or eliminates the need for enzymes or other additives, removes trypsin inhibitors and addresses the negative impact of oxidative processing environments.